This research proposal is concerned with the synthesis, structure and properties of specific iron and molybdenum complexes. These compounds will be obtained employing ligands which are specifically chosen to simulate the proposed or known protein structure at the active sites of several nitrogenases and ferredoxins. Structural and bonding information on the active site analogs will be obtained by means of X-ray diffraction, magnetic susceptibility electron spin resonance and Mossbauer techniques. Comparative studies between the actual metalloenzymes and appropriately designed active site analogs will be conducted and the results will be correlated with existing proposals concerning enzymic action. The effect of the ligands on the electrochemical properties of the complexes will be examined in detail in order to understand the redox properties of more complicated enzymatic systems of biochemical importance. Thus far the complexes ((C6H5S)2 FeS2MS2)2-, ((S5)FeS2MS2)2-, ((Cl2Fe)2S2MS2)2-, ((MS4)2Fe)3-, ((NO)2FeS2MS2)2-, (Cl2FeS2MS2)2-, and (Fe(WS4)2 2DMF)2- (M equals Mo,W) have been synthesized, structurally characterized and investigated in detail. At present the redox properties and reactivities of these species are under study.